So wait.
Assume Hopey adopts Bob as his father, son, brother, and uncle. Then Bob marries Alice (making her a stepmother, sister-in-law, aunt, and daughter-in-law). Bob and Alice have a child, named Candice.
Candice is now Hopey's stepsister, niece, granddaughter, and cousin, without ever having been directly adopted.
If Hopey now adopts Candice as his sister, daughter, mother and aunt, he becomes related to her in eight separate ways, and it is legally considered incest for them to be in the same room.
If Hopey then retroactively adopts Alice as a sister-daughter-mother-aunt, Candice's family tree implodes into being a family tumbleweed, and Candice herself becomes a five-eyed Lovecraftian horror known only as "Scion of the Hopeless".
We must take drastic measures to ensure that this being never awakens.
edited 10th Aug '13 4:23:49 PM by Muramasan13
Smile for me!

Oh, c'mon.
Now you know that's both impossible and possible.